The performance of a typical antenna may be greatly affected by the surface onto which it is mounted. Therefore, most antenna designs take into account the material of the surface onto which the antenna will be mounted. For example, a typical antenna that will be placed onto a metal box may be designed for optimal performance knowing that the metal box will affect the operation of the antenna. However, if that same antenna is placed on a wooden box, or in free space, the antenna will operate in a much different, non-optimal, way.
Further, conformal antennas on metals, in general, tend to provide relatively poor performance with very weak efficiencies (less than 40%). Patch antennas, in contrast, exhibit good efficiency numbers while being very conformal, but they suffer from the drawback that the peak gains usually are higher than 4 or 5 dBi. Such a peak gain causes problems for FCC compliance purposes. Peak gain of patch antennas can be reduced by reducing their efficiencies, such that patch antennas have very poor performance. Designing multiband antennas is also a big challenge for patch antennas. Patch antennas are not omni-directional and are not favored in applications where RF power needs to be distributed adequately in all directions.
Therefore, for applications requiring high-performance, multiband operation, patch antennas are usually not an option. Even more difficult are those same applications where the antenna may be mounted on a variety of surface materials.